Rolling mill apparatus



' Oct. 12, 1965 N. H. POLAKOWSKI 3,210,

ROLLING MILL APPARATUS Filed Oct. 16, 1961 2 Sheets-Sheet 1 I INVENTOR. FI 2 I JVaZalzs JiPoZakows/cz Oct. 12, 1965 N. H. POLAKOWSKI ROLLING MILL APPARATUS 2 Sheets-Sheet 2 Filed Oct. 16, 1961 m w m m Nata/i5 1f Poia/(aws/ez United States Patent 3,210,982 ROLLING MILL APPARATUS Natalis H. Polakowski, 500 Kin Court, Wilmette, Ill. Filed Oct. 16, 1961, Ser. No. 145,351 3 Claims. (Cl. 72-201) This invention relates to improvements in rolling mills, and it relates more particularly to improved means for reducing the thickness of flat products including foil, strip, sheet and plate by hot and cold rolling techniques.

It is well known that when products of the above types are rolled in continuous lengths in present rolling mills it is extremely difiicult to maintain the products perfectly flat. The degree of flatness can be demonstrated by observing the occurrence of waves, buckles and Warped portions in the rolled products. The presence of such defects occurs when certain portions of the longitudinal material elongate during rolling to a different degree than adjoining portions. Such differential elongation can occur in rolled products irrespective of the absolute thickness of the metal in a given section and, therefore, flatness will not always depend on variations in thickness in a given product section. With differential elongation, waves, buckles and Warped portions will occur even with absolutely uniform finished thickness.

In the continuous rolling of wide strip, ideally flat conditions have been approached by modifying the roll design. Thus, so-called cambering of the rolls, whereby the rolls are ground to a different diameter at the center to compensate for bending and thermal expansion, provides improved flatness. Furthermore, careful rolling techniques can provide flat products, but cambering and improved rolling techniques have limited practicality. Such techniques, for example, are only relatively satisfactory where coils containing at times miles of strip in continuous lengths are being rolled. With such large coils the speed of rolling is high and the working rolls will heat up considerably due to the combined effect of work and friction between the coil and the working rolls. Heating of the massive rolls will result in their expansion, particularly in a radial direction and, due to the variable cooling conditions along the roll barrels, the mid-length portions thereof will generally become hotter than the ends. These temperature gradients accordingly result in the application of more pressure on the product being rolled in certain localities and, therefore, the product will elongate more in these localities. As a result, buckling, waving and warping of the sheet occurs.

Such conditions are partially remedied in practice by means of cooling sprays applied to the roll surfaces. Such sprays are not completely effective, particularly where materials such as mineral oil must be used for cooling and lubrication. These materials have a relatively low cooling ability and the undesirable differential expansion cannot be avoided in many cases. The above is also true in mills with thin work rolls which heat up rapidly and produce varying degrees of reduction across the width of a plate or sheet. The limited surface area of these rolls which is exposed to the coolant prevents efficient cooling, and there is a consequent development of excessive temperature variations. The heat camber produced in the working rolls will thus result in waviness due to the differential elongation across the strip.

Apart from the use of selective cooling, other attempts have been made to compensate for transient diameter changes in the working rolls. Thus, mechanical means have been applied to the rolls in such a manner as to counteract any curvatures developed by thermal gradients. Such means have been review in an article entitled Control of the Shape of Metal Strip by Camber Variation During Rolling, by Singer in Sheet Metal Industries, February 1959, pp. 184-189. The mechanical means re- 3,210,982 Fatented Oct. 12, 1965 "ice viewed in the article and others available in the prior art have, however, not proven successful and have not been adopted by industry to any significant extent.

It is an object of this invention to provide an improved rolling mill apparatus which will enable the production of effectively fiat mill products.

It is a related object of this invention to provide efficient means for avoiding the detrimental effects of roll temperature build up and temperature differentials which occur in the rolling of metal strip, foil, sheet and plate.

These and other objects of this invention will appear hereinafter and, for purposes of illustration, but not of limitation, specific embodiments of this invention are shown in the accompanying drawings in which:

FIGURE 1 is a plan view of a portion of a rolled sheet illustrating the detrimental effects of uneven rolling;

FIGURE 2 is an elevational view of a 4-high mill characterized by the features of this invention;

FIGURE 3 is a vertical section of the 4-high mill shown in FIGURE 2; and

FIGURE 4 is a side elevation, partly in section, of a 3-high mill provided with certain improvements of this invention.

The problems which are presently encountered in the rolling of metal by known techniques can be illustrated by considering the sheet section shown in FIGURE 1. The sheet 10 shown, although having a uniform thickness has passed from a rolling mill with wavy edges 12, slight- 1y exaggerated for purposes of illustration. If a sheet of this type were slit to provide strips 14 through 22, the stresses within the sheet would result in considerable bowing of the outside strips 14 and 22. Thus, where the working rolls produce insufficient crowns in operation the center of the sheet will become elongated to a lesser eX- tent than the sides thereof, and the final product will have wavy edges. If the sheet is slit in the manner shown, the residual stresses in the outside strips will cause substantial elimination of the wavy edges, but a permanent distortion in these strips will result. Obviously, there will be a tendency for the strips 16 and 20 to similarly distort, although in a less pronounced manner.

In accordance with the techniques of this invention, a sheet is produced whereby uniform elongation will be provided across its width and, therefore, wavy edges and buckled centers will not result and, without unbalanced residual stress, slitting will not result in bowing or other distortion in strips.

Broadly, the means which are employed for achieving the above objects consist in mechanisms for controlling the crown or camber produced in Working rolls during rolling. Specifically, means are provided for effectively and rapidly offsetting the dimensional changes which tend to occur in working rolls. The mechanisms of this invention provide for intentionally induced dimensional changes in a hard, cylindrical sleeve which loosely surrounds a supporting roll and which frictionally engages the supporting roll on its inner surface and a Working roll on its outer surface. The inside diameter of the cylindrical sleeve is larger than the outside diameter of its supporting roll by a margin which varies from a small fraction of an inch to several inches or more, depending on various requirements. The cylindrical sleeve is made of a hardened steel or other rollmaking material, and the dimensional changes which are intentionally induced in the sleeve are provided for inducing corresponding changes in the working roll which the sleeve engages. By selectively inducing dimensional changes in the sleeve in accordance with tendencies for dimensional changes in a working roll, the changes in the working roll profile can be effectively offset and the rolls will, therefore, not produce variable percent elongation across the product being worked.

The length of the cylindrical floating sleeve is preferably substantially identical with that of its supporting roll, although narrower sleeves could be employed when large quantities of narrow strip are to be rolled. The thickness of the sleeve is determined by various practical factors relating to life expectancy and rigidity of the sleeve and to production requirements.

Dimensional changes in accordance with the present invention can be induced in the sleeve by selective heating or cooling of the relatively thin-walled sleeve. The thickness of the sleeve can thus be caused to increase or decrease slightly in a preselected area, and it is obvious that a thickness increase in the sleeve will transmit pressure to the working roll which will accordingly locally increase the working pressure on the sheet. It is also contemplated that the sleeve of this invention can be utilized in a 2-high mill whereby the sleeve will be in direct contact with the material being worked.

Localized cooling of the sleeve of this invention will obviously produce a result opposite to localized heating. Thus, differences in elongation which cause the type of defects illustrated in FIGURE 1 can be eliminated by selecting the position and intensity of heating and cooling across the length of the sleeve. In order to determine the degree of heating or cooling necessary, it must be noted that very small differences in reduction, on the order of .01 to .l%, will produce distinct, measurable and readily visible level differences across a sheet or strip.

The thermal expansion coefficient of steel is about 7 10 which means that a 50 F. increase of temperature in a sleeve 4 inches thick will result in a linear expansion of about 0.0015 inch across its thickness. In a mill with a modulus of about 40,000 tons per inch extension, the resulting change of separating force would be 120,000 lbs., which is about of the normal separating force in rolling ordinary tinplate. In a foil mill with a 7,000 ton per inch modulus, the same expansion in a sleeve will increase the separating force by about 20,000 lbs., or by the equivalent of 7 to 10% of the separating force encountered in rolling 40 inch wide foil. Obviously, for corrective purposes, uniform expansion along the entire length of a sleeve is not necessary. However, the corresponding forces per unit Width of rolled sheet should be proportional to the values stated above, and these values illustrate a basis for providing the necessary corrections which can be accomplished by selective heating or cooling.

In ordinary rolling mill operations, temperature changes in the rolls are gradual rather than sudden due to the large cross-section and masses of the rolls. With a sleeve of the type of this invention, temperature changes can be effected rather quickly since the wall thickness of the sleeve is relatively small and a large exposed area is available for the application or extraction of heat. At the same time, the portion of the sleeve in direct contact with the material being rolled or in contact with the work roll pro vides a massive force transmitting body substantially equivalent to a working roll or backup roll of similar diameter.

In applying the principles of this invention, it is pointed out that the provision of the cylindrical sleeves is not limited to a single side of a mill. Thus a pair of the sleeves can be employed to provide the two working surfaces in a mill, the sleeves could be employed over backup rolls for independent working rolls or a combination of these conditions could be provided. Obviously, the sleeves can be used in existing rolling mills with a minimum of structural change and, since the sleeves considerably reduce the unit pressure on the surface of their supporting rolls, supporting rolls softer than is conventionally accepted can be employed. The sleeves can be manufactured with a more uniform hardness in view of the relative thinness thereof and, therefore, they are characterized by improved fatigue life and reduced spalling tendencies. The sleeves can be more rapidly cooled, since both external and internal surfaces are available for this purpose and, since an open space is provided between the sleeve and its supporting roll, the inner surface can be utilized for heat transfer by providing heating and cooling elements within this space as well as adjacent the outer sleeve periphery. The invention also contemplates the provision of radially or obliquely oriented holes in the sleeve for cooling purposes.

The accompanying drawings illustrate exemplary and typical embodiments of this invention. FIGURE 2 shows the application of a single camber control sleeve to a typical 4-high strip or sheet mill. A supporting roll 24 is provided at the top of the mill and a backup roll 26 is provided in the mill on the opposite side of the working rolls 28. A sheet 30 is provided for passage through the working rolls 28 in a conventional manner.

A cylindrical camber control sleeve 32 is positioned around the supporting roll 24 and the combination provides a backup means for the upper working roll 28. Induction heating coils 34 and 36, energized through leads 38 and 40, are shown located adjacent the outer periphery of the sleeve 32 near the ends thereof. Cooling means for the sleeve are provided by nozzles 42 and 44 which eject cooling liquid 46 onto the sleeve surface in the center portion. The heating and cooling means are preferably arranged to move transversely of the sleeve axis and obviously additional heating and cooling means of like kind can be provided. The particular positioning of the heating and cooling means illustrated is preferred since the center portion of the working and backup rolls generally becomes heated to a greater extent than the side portions thereof. Thus, the placement of the heating and cooling means will serve to balance the temperature across the sleeve.

It will be noted that a substantial space is provided between the sleeve 32 and the supporting roll 24. Accordingly, the inner surface of the sleeve can be utilized for heat transfer by placing heating and cooling elements within this open space. Such elements can complement the elements on the outer periphery of the sleeve or be provided as the sole temperature control means.

FIGURE 4 illustrates an arrangement wherein mechanical means are provided for producing a variable and adjustable pressure upon the sleeve body, at different locations. With such an arrangement a corrective force can be indirectly applied to a work roll in contact with the camber control sleeve, or the corrective force can be applied directly to the material being worked if the sleeve serves as the Working roll. The mechanical means illustrated work independently of the sleeve temperature control arrangement, although serving essentially the same purposes. It will be apparent, however, that the mechnical means can be employed along with the temperature control means.

FIGURE 4 illustrates a 3-high sheet mill 50 carrying a pair of large rolls 52 and 54 and a baby roll 56. The sheet 58 is reduced by passage through the rolls 54 and 56 as is typical in a 3-high mill. The rolls 52, 54 and 56 are conventionally mounted in respective chocks 60, 62 and 64, and the camber control sleeve 66 of this invention is supported by the roll 52. A screw 68 and associated wheel 70 provide a screw down gear for producing the major pressure on the sheet during working.

Additional pressure for avoiding camber and other defects during operation is exerted upon the sleeve 66 by means of rollers 72 and 74 which are respectively mounted on axles 76 and 78. The axles ride in bifurcate lever arms 80 and 82 of the L-shaped rocking levers 84 and 86. These levers are mounted for swinging within limited angles on stationary axles 88 and 90. The axles in the illustration shown also act as tie rods between the two mill housing frames. An adjusting spindle 92 with a left hand thread at one end and a right hand thread at the other end passes freely through holes or slots 94 and 96 formed in the upper ends of the levers 84 and 86. Nuts 98 and 100 are screwed onto the spindle 92 and are provided with spherical surfaces for interfitting with corresponding recesses 102 and 104 in the levers 84 and 86. The spindle 92 is provided with a hand wheel 106.

Rotation of the wheel 106 will cause the levers 84 and 86 to swing inwardly or outwardly on the axles 88 and 90. The force exerted by the rollers 72 and 74 upon the surface of the sleeve 66 will, accordingly, be increased or decreased depending upon the direction of rotation of the wheel 106. The face width of the rollers 72 and 74 is only a fraction of the length of the sleeve 66 and, therefore, the force application by the rollers will be applied only in a limited area of the sleeve 66. Accordingly, only a section of the working roll 56 will be principally affected by the application of force to the relatively flexible sleeve 66. It will be apparent that several pairs of the force applying press rollers 72 and 74 can be positioned transversely of the sleeve surface, and each pair can be provided with individual adjusting means. In addition, the press rolls 72 and 74 need not be arranged symmetrically with respect to vertical planes passing through the supporting roll axis. An asymmetrical arrangement can be provided by altering the ratio of the arms of the L levers 84 and 86 on either side of the sleeve, or by altering the position of the fulcrum pivot 88 or 90.

Obviously, the adjusting spindle 92 can be driven mechanically rather than manually. The spindle can be readily replaced by a hydrauliccylinder which will perform the same basic function with respect to the sleeve 66. In this connection the means for controlling the mechanical rollers 72 and 74 as well as the means for controlling the temperature control" elements previously described can be automatically actuated in accordance with variations in the strip being produced. Thus, it is Well known in the art to provide means for measuring material issuing from a rolling mill and for automatically initiating changes in the roll spacing, etc. Such automatic means could be employed for initiating desired changes in the temperature control and mechanical systems of this invention.

The camber control sleeve is preferably provided from a single cylinder, however, two or more shorter sleeves jointly covering a supporting roll can be employed. This arrangement will be advantageous when it is desired to rely principally upon mechanical means for controlling camber in a working roll. Thus, separate control units can be employed for each of the sleeve portions and increase or decrease in pressure on one portion will not influence pressure on an adjoining portion.

The sleeve can be secured against drifting along the roll by suitable stop rollers (not shown) mounted upon the mill frame and bearing against the flat end faces of the sleeve. Alternatively, rims can be provided at both ends of the sleeve construction for straddling the supporting roll or the adjoining working roll to maintain the construction in position.

The apparatus of this invention has provided thermal and mechanical means for jointly or individually altering the dimensions of a cylindrical sleeve in order to compensate for any tendency for dimensional changes in the apparatus which would result in undesirable mill products. The installation of the camber control sleeves of this invention will not in any way obstruct the accessability of working rolls in the bite area. The described apparatus is inexpensive and characterized by simplicity insofar as the particular thermal and mechanical control means are concerned. The camber control technique described is applicable to various existing mills, including 2-high, 3-high and 4-high mills, cluster type mills and other mills employed either for hot or cold rolling of metal. The technique has been found particularly suitable in the rolling of thin, fiat products in long lengths, such as tinplate, steel and aluminum foil. Suitability for the production of thin products is obvious since it is in these products that the problems of warping, buckling and Waving having been most pronounced.

It will be understood that various modifications may be made in the above described apparatus which provide the characteristics of this invention without departing from .the spirit thereof, particularly as defined in the following claims.

I claim:

1. In apparatus for the rolling of metal including a pair of rolls between which the metal passes for reduction of the thickness thereof, the improvement comprising camber control means associated with one of said rolls, said control means comprising a back-up for one of said rolls and including a supporting roll, an annular sleeve disposed about said supporting roll, said sleeve having an inner diameter greater than the outer diameter of said supporting roll and being mounted for contact with said one roll, and means positioned at a plurality of points adjacent the surface of said sleeve for controlling the pressure of said sleeve on said one roll during a rolling operation by elfecting distortion in small areas of said sleeve to effect control of said sleeve pressure in correspondingly small areas of said one roll.

2. An apparatus according to claim 1 wherein said pressure controlling means include heating means positioned adjacent the ends of said sleeve and cooling means positioned centrally of said sleeve.

3. An apparatus according .to claim 1 wherein said pressure controlling means include a plurality of press rollers engaging the outer periphery of said sleeve and means for individually adjusting the force with which said press rollers engage said sleeve whereby the pressure of said sleeve on said one working roll can be selectively controlled.

References Cited by the Examiner UNITED STATES PATENTS 626,847 6/99 Theobald -41 1,516,612 11/24 McIntosh 80-41 1,581,218 4/26 Maguire 80-41 1,953,190 4/34 Paterson 80-41 2,133,051 10/38 Bollinger 80-31.1 2,181,173 11/39 Catulle 80-38 2,187,250 1/40 Sendzimir 80-38 2,344,274 3/44 Stacom 80-38 2,677,978 5/54 Dahlstrom 80-38 2,792,730 5/57 Cozzo 80-56 3,049,950 8/62 Pearson 80-56.2

FOREIGN PATENTS 48,834 3/21 Sweden.

WILLIAM J. STEPHENSON, Primary Examiner. LEON PEAR, Examiner. 

1. IN APPARATUS FOR THE ROLLING OF METAL INCLUDING A PAIR OF ROLLS BETWEEN WHICH THE METAL PASSES FOR REDUCTION OF THE THICKNESS THEREOF, THE IMPROVEMENT COMPRISING CAMBER CONTROL MEANS ASSOCIATED WITH ONE OF SAID ROLLS, SAID CONTROL MEANS COMPRISING A BACK-UP FOR ONE OF SAID ROLLS AND INCLUDING A SUPPORTING ROLL, AN ANNULAR SLEEVE DISPOSED ABOUT SAID SUPPORTING ROLL, SAID SLEEVE HAVING AN INNER DIAMETER GREATER THAN THE OUTER DIAMETER OF SAID SUPPORTING ROLL AND BEING MOUNTED FOR CONTACT WITH SAID ONE ROLL, AND MEANS POSITIONED AT A PLURALITY OF POINTS ADJACENT THE SURFACE OF SAID SLEEVE FOR CONTROLLING THE PRESSURE OF SAID SLEEVE ON SAID ONE ROLL DURING A ROLLING OPERATION BY EFFECTING DISTORTION IN SMALL AREAS OF SAID SLEEVE TO EFFECT CONTROL OF SAID SLEEVE PRESSURE IN CORRESPONDINGLY SMALL AREAS OF SAID ONE ROLL. 